Heat-radiating component and method of manufacturing the same

ABSTRACT

A heat-radiating component includes a wick layer formed on an inner wall of a hermetically sealed container made of metal and a working fluid encapsulated in the hermetically sealed container. In the wick layer, micro carbon fiber is mixed into metal powder. In one aspect, the wick layer is a structure combined by a first wick and a second wick, the first wick being formed of sintered metal powder, and the second wick being a plating layer into which micro carbon fiber is mixed so as to partially fill air space inside the first wick while covering a surface of the first wick. The first wick is preferably a body sintered copper powder, and the second wick is preferably made of a copper plating layer into which carbon nanotube or carbon nanofiber is mixed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of theprior Japanese Patent Application No. 2009-271445, filed on Nov. 30,2009, the entire contents of which are incorporated herein by reference.

FIELD

The embodiments discussed herein are related to a heat-radiatingcomponent and a method of manufacturing the same. More particularly,they relate to a heat-radiating component such as a heat pipe or thelike used in cooling a heat-generating component such as a CPU embeddedin a personal computer, an electronic device or the like, and also to amethod of manufacturing the same.

BACKGROUND

The heat pipe has advantages in that the heat pipe can use CFC-freewater for the working fluid (refrigerant), and does not require externalpower, for example. The heat pipe is widely used as a heat-radiatingcomponent for a large capacity power semiconductor (thyristor, diode,power module and the like), an MPU for a computer server, a hermeticallysealed chassis for a control panel of a machine tool or the like. Theheat pipe is increasingly used as a cooling component for aheat-generating component (a semiconductor element or the like such as aCPU, which is required to operate at higher speed along with higherintegration of chips, and which thus generates a large amount of heat)embedded in a small electric device such as a notebook PC.

As heat pipes used in the aforementioned field, heat pipes small in sizeand diameter become mainly used along with reduction in size ofelectronic devices. In addition, flat heat pipes have been preferablyused. This is because a flat heat pipe can be easily installed onto acomponent (such as a CPU) to be cooled, and also, a wide contact surfacecan be obtained.

As a structure of the heat pipe, various types have been proposedheretofore. In the basic structure of a heat pipe, a working fluid(typically, water) encapsulated inside a hermetically sealed pipe isevaporated (latent heat absorption) by externally heating one end(heating portion) of the pipe, and steam thus generated moves to a lowtemperature portion at the other end of the pipe. Then, the steam iscondensed (latent heat release) at this portion, and the condensedworking fluid returns to the heating portion along the inner wall of thepipe. The portion along which the working fluid returns (the inner wallof the pipe) is provided with a capillary structure called a “wick.” Thewick is provided in various forms including a bundle of metal wires, ametal mesh, grooves and a sintered body of metal powder.

Among the aforementioned forms, a groove heat pipe is the mainstream.The groove heat pipe is excellent in the heat resistance (heatconductivity) of the pipe material itself, but has a problem of beingpoor in inclination dependency (i.e., heat transportation by theinclined heat pipe is not sufficient) because the capillary forcethereof is lower than those of the other types. For example, in a casewhere the groove heat pipe is embedded in a notebook PC often tilted atthe time of usage, the groove heat pipe can transport heat onlyinsufficiently and itself cannot be cooled so much due to its lowcapillary force. Thus, a sufficient cooling effect cannot be expected.

To solve this problem, a sintered metal heat pipe (a sintered body ofcopper powder or the like is formed on the inner surface of the pipe)has been developed in recent years. Having a high capillary force, thesintered metal heat pipe is expected as one possible solution for theinclination dependency.

As a technique related to such conventional art, there is anelectrically insulated heat pipe described in Patent Document 1 below,for example. In addition, Patent Document 2 below describes a techniquefor a heat pipe in which water is encapsulated as a heat medium inside acontainer made of copper or copper alloy, and in which an oxide filmwith a thickness of a predetermined value or less is formed on a contactsurface of the container with the heat medium. In addition, a flat heatpipe described in Patent Document 3 below is cited as an example.Moreover, an example of the technique related to the wick using sinteredmetal is described in Patent Document 4 described below. Further, asdescribed in Patent Document 5 below, there is a heat pipe using wateras the working fluid and having an inner surface formed of Ni-base alloyand plated with Cu.

-   Patent Document 1: Japanese Laid-open Patent Publication No. 4-98093-   Patent Document 2: Japanese Laid-open Patent Publication No.    9-113162-   Patent Document 3: Japanese Laid-open Patent Publication No.    2009-180437-   Patent Document 4: Japanese Laid-open Patent Publication No.    2007-56302-   Patent Document 5: Japanese Laid-open Patent Publication No. 7-90534

As described above, the conventional wick structure employing sinteredmetal uses copper powder as the metal powder to be sintered. Thus, thefollowing problems exist when copper powder is sintered.

First, one of the problems is that the facility cost is high. This isbecause, for a heat pipe made of copper, for example, sintering in aninert gas (such as nitrogen gas or argon gas) atmosphere needs to beperformed under a high temperature (about 900 to 1050° C.). In addition,the pipe material (copper) easily causes crystal grain coarsening anduneven deformation during the sintering. Thus, there arises anotherproblem that a bending process and flattening process performedthereafter is difficult.

Moreover, there is still another problem that it is difficult to obtainan ideal wick layer (wick layer having a high capillary force and a lowflow path resistance that allows the working fluid to easily flowthrough the path) because the average grain size of copper powder in useis approximately the same. Specifically, when the grain size of copperpowder is small, a gap between adjacent grains is small. Thus, a highcapillary force can be obtained in this case but the circularity of theworking fluid deteriorates corresponding to the smallness of the gap.Meanwhile, if the grain size of the copper powder is large, the gapbetween adjacent grains is large. Thus, the circularity of the workingfluid improves in this case but a high capillary force cannot beobtained.

In addition, when metal powder such as copper powder is sintered, airspace is formed on crystal grain boundaries of the sintered body (seeFIG. 4C). It is generally said that the electric conductivity and heatconductivity of the sintered body are lower than those of a bulk metal(bulk of metal such as copper or the like) with approximately the samesize as the sinter body. There is a literature indicating that the heatconductivity of copper powder before being sintered is 0.14 to 0.18W/(m·K). Accordingly, when a sintered body of metal powder is used for awick, the heat conductivity of the heat pipe using such wick often islower than that of a groove heat pipe in which the unpowdered pipematerial (copper) is processed.

In the technique disclosed in Patent Document 4 described above, asintered wick layer of a heat pipe with a good productivity, a highcapillary force, and an excellent circularity of working fluid has beenproposed. This sintered wick layer of the heat pipe is obtained byheating and sintering, under a reducing atmosphere, an unsintered wicklayer formed by using two types of copper powder.

However, the sintered metal is also used as the wick in the techniquedisclosed herein. Accordingly, it is considered that the heat pipe usingthis wick is inferior in the heat resistance (heat conductivity) to thegroove heat pipe, which is obtained by processing an unpowdered coppermaterial.

SUMMARY

According to one aspect of the invention, there is provided aheat-radiating component including a hermetically sealed container madeof metal, a wick layer formed on an inner wall of the hermeticallysealed container, and a working fluid encapsulated in the hermeticallysealed container, wherein micro carbon fiber is mixed into metal powderin the wick layer.

According to another aspect of the invention, there is provided a methodof manufacturing a heat-radiating component which includes a wick layerformed on an inner wall of a hermetically sealed container made of metaland which encapsulates a working fluid in the hermetically sealedcontainer, the method including forming the wick layer, wherein theforming the wick layer includes mixing micro carbon fiber into metalpowder.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view for explaining operational effects of a heat pipeincluding a sintered metal wick (capillary structure);

FIG. 2A is a vertical cross-sectional view showing a configuration of aheat pipe according to an embodiment, FIG. 2B is an enlargedcross-sectional view of a portion (evaporating portion) in FIG. 2A, andFIG. 2C is an enlarged cross-sectional view of a portion (wick layer)denoted by reference sign A in FIG. 2B;

FIG. 3A is a view for explaining effects obtainable by the heat pipeillustrated in FIGS. 2A to 2C in comparison with the case of a relatedart (FIG. 3B);

FIG. 4A is a vertical cross-sectional view showing a configuration of aheat pipe according to a modification of the embodiment illustrated inFIGS. 2A to 2C, FIG. 4B is an enlarged cross-sectional view of a portion(wick layer) denoted by reference sign A in FIG. 4A, and FIG. 4C is anenlarged cross-sectional view of a portion (sintered wick layer) denotedby reference sign B in FIG. 4A; and

FIG. 5A is a diagram showing an application example of a vapor chamberaccording to another embodiment, FIG. 5B is a vertical cross-sectionalview showing a configuration of the vapor chamber in FIG. 5A, and FIG.5C is an enlarged cross-sectional view of a portion (wick layer) denotedby reference sign A in FIG. 5B.

DESCRIPTION OF EMBODIMENTS

Hereinafter, preliminary matters for a better understanding ofembodiments are described before explaining the embodiments.

(Preliminary Matters; See FIG. 1)

FIG. 1 is a diagram showing an example of a heat pipe including asintered metal wick (capillary structure). In the illustrated heat pipe10, a hermetically sealed metal pipe 12 has a shape processed into aflat shape in a cross-sectional view. In addition, a sintered wick layer14 is formed on an inner wall surface of the metal pipe 12. Further, anappropriate amount of water 16 (vaporized water W1 illustrated by white∘ and condensed water W2 illustrated by black •, which are schematicallyexpressed at the molecular level in the illustrated example) is vacuumencapsulated in the metal pipe 12 as the working fluid.

While the heat pipe 10 functions, the working fluid (water 16) isexternally heated and thus evaporated at one end (evaporating portion atthe left end portion in the illustrated example), and then, steam W1 ofthe evaporated working fluid moves to the other end (condensing portionat the right end portion) in the pipe 12. Then, the steam W1 iscondensed at the condensing portion. In addition, the condensed water W2moves to the one end via the wick layer 14 on the inner wall surface ofthe pipe 12. Thus, the working fluid refluxes in the pipe 12 byrepeating the aforementioned movement.

The sintered wick layer 14 formed on the inner wall surface of the metalpipe 12 is obtained by, for example, depositing copper powder to arequired thickness on a surface of a metal plate made of copper orcopper alloy (metal plate before being subjected to a bending process,flattening process and the like to form the metal plate into a requiredmetal pipe shape) and then heating and sintering the resultant object.Here, when viewed microscopically, the cross-sectional structure of thesintered wick layer 14 has a structure in which grains of copper powdergrain having the approximately same average grain size are partially incontact with each other as if pebbles are stacked (see FIG. 4C, forexample). In other words, a gap (air space) exists between grains (ofcopper powder).

As described above, in the wick structure using the sintered metalaccording to the current technique, copper powder is used as the metalpowder to be sintered. Accordingly, there arise various problemsdescribed above when the powder is sintered.

Hereinafter, the embodiments are described.

First Embodiment

FIGS. 2A to 2C are diagrams showing a configuration of a heat pipeaccording to an embodiment. FIG. 2A shows a vertical cross-sectionalstructure of the heat pipe 20. FIG. 2B shows an enlarged cross-sectionalstructure of a portion (evaporating portion) in FIG. 2A. FIG. 2C showsan enlarged cross-sectional structure of a portion (wick layer 24)denoted by reference sign A in FIG. 2B.

The heat pipe 20 according to this embodiment includes a hermeticallysealed metal pipe 22 as illustrated. The metal pipe 22 has a shapeprocessed into a flat shape in a cross-sectional view. The wick layer 24(capillary structure) is formed on an inner wall surface of the metalpipe 22. Further, a working fluid is vacuum encapsulated in the metalpipe 22 as the heat medium.

As the material of the metal pipe 22, a material excellent in heatconductivity is preferable, and copper or copper alloy (such aslow-oxygen copper or oxygen-free copper, for example) is preferablyused. In this case, an appropriate amount of water is sealed inside themetal pipe 22 as the working fluid. In particular, pure water such asion exchange water or distilled water is preferred in that such water isunlikely to cause an electrochemical reaction. Although not illustratedin FIGS. 2A to 2C, the working fluid (water) refluxes in the pipe asillustrated in FIG. 1, while the heat pipe 20 functions. Specifically,the working fluid moves inside the metal pipe 22 from one end(evaporating portion) to the other end (condensing portion), and thenmoves from the other end (condensing portion) to the one end(evaporating portion) via the wick layer 24, thus refluxing in the pipe22 by repeating the aforementioned movement thereafter.

Note that, the material of the metal pipe 22 is not limited to copper orcopper alloy as a matter of course, and other materials can be used asappropriate.

The wick layer 24 formed on the inner wall surface of the metal pipe 22has a structure in which two types of wicks are combined. A first wickis a copper powder sintered body (sintered wick layer) 26 obtained bysintering copper powder. A second wick is a copper plating layer 28 a inwhich carbon nanotube (CNT) or carbon nanofiber (CNF) 28 b is mixed.This copper plating layer 28 a in which CNT (or CNF) 28 b is mixed ishereinafter referred to as a “CNT mixed copper plating wick layer 28,”or simply, “plating wick layer 28” for the sake of convenience.

The sintered wick layer 26 (first wick) is equivalent to the sinteredmetal wick formed by using the current technique (sintered wick layer 14of FIG. 1). Accordingly, when the cross-sectional structure of thesintered wick layer 26 is viewed microscopically, the sintered wicklayer 26 has a structure in which grains of copper powder 26 a havingthe approximately same average grain size are partially in contact witheach other as if pebbles are stacked (see FIG. 4C, for example). Inother words, air space exists between the grains (copper powder 26 a).

The CNT mixed copper plating wick layer 28 (second wick) is formed byapplying, copper plating in which CNT (or CNF) is mixed, onto thesurface of the sintered wick layer 26 as described later. As illustratedin FIG. 2C, this plating wick layer 28 is formed to cover the surface ofthe sintered body (surface portion of the sintered wick layer 26) whilefilling the air space inside the sintered wick layer 26. When theplating wick layer 28 is formed, adjustment is important such that theplating wick layer 28 fills the air space inside the sintered wick layer26 not completely but partially.

In the example illustrated in FIG. 2C, the state where the air space inthe copper powder sintered body 26 is completely filled with the platingwick layer 28 is illustrated. However, slight air space is left in partof the air space, actually. Such slight air space is left in the wicklayer 24 to maintain a required capillary force.

Next, a method of forming the wick layer 24 in particular is describedin a method of manufacturing the heat pipe 20 of the embodiment.

As one method, a metal plate having a size necessary for forming themetal pipe 22 is first prepared. Specifically, what is prepared here isa metal plate before being subjected to a bending process, flatteningprocess and the like to be formed into a required shape as the metalpipe 22 in which a working fluid is eventually encapsulated andhermetically sealed. As the material of this metal plate, copper orcopper alloy excellent in heat conductivity is preferably used.

Next, copper powder is deposited on one of surfaces of the metal plate(copper plate) to a required thickness. Then, the resultant object isheated and sintered. Accordingly, the sintered wick layer (copper powdersintered body) 26, which is the first wick, is formed (the stateillustrated in FIG. 4C).

Next, copper plating in which CNT (or CNF) is mixed is applied onto thesurface of the sintered wick layer 26. Accordingly, the CNT mixed copperplating, wick layer 28, which is the second wick layer, is formed (thestate illustrated in FIG. 2C).

As the plating solution used for forming the plating wick layer 28, acopper plating solution in which CNT (or CNF) is dispersed by usingprotein as a dispersing agent is preferably used, for example. Here, useof protein (gelatin, collagen peptide or the like) as a dispersing agentimproves the dispersibility of CNT, thus enabling an improvement in theflatness of the plating film to be formed (achieving uniform filmthickness). In addition, application of ultrasonic wave in dispersingCNT (or CNF) further enables the improvement in the dispersibility.

When the CNT mixed copper plating is applied onto the copper powdersintered body (sintered wick layer) 26, the copper plating solution alsoenters the air space inside the copper powder sintered body 26 (copperplating layer 28 a is formed on the surfaces of the copper powder 26 a)as illustrated and functions so as to fill the air space. However, ifthe air space is completely filled, the capillary force of the wicklayer 24 is reduced.

Accordingly, when the CNT mixed copper plating is applied, the platingtime needs to be appropriately adjusted such that the air space insidethe copper powder sintered body 26 is partially filled (specifically,slight air space to maintain sufficient capillary force is left). Forexample, when the size of a grain of the copper powder 26 a is 100 μm,the thickness of the plating (plating wick layer 28) applied to thesurface of the sintered body is set approximately equal to or less than30 μm.

While the heat pipe 20 of the embodiment functions, the heat generatedin the metal pipe 22 due to the heat supplied from the outside (from asemiconductor element generating heat such as a CPU) is conducted to theworking fluid (water in this case) in the metal pipe 22 via the wicklayer 24 (structure in which the sintered wick layer 26 and the CNTmixed copper plating wick layer 28 are combined). Accordingly, the waterin the corresponding portion (evaporating portion) inside the pipe 22 isevaporated. Then, the steam moves to the low temperature portion(condensing portion), which is at the end opposite from the evaporatingportion inside the pipe 22, and is then condensed at the low temperatureportion. Moreover, the condensed water returns to the one end via thewick layer 24 on the inner wall surface of the pipe 22 and then refluxesin the pipe 22 by repeating the aforementioned movement.

As described above, with the heat pipe 20 according to this firstembodiment and the method of manufacturing the same, the CNT mixedcopper plating wick layer 28 is formed on the copper powder sinteredbody (sintered wick layer) 26 formed on the inner wall surface of themetal pipe 22 as follows. Here, the CNT mixed copper plating wick layer28 is formed to partially fill the air space (gaps between grains of thecopper powder 26 a) inside the copper powder sintered body 26 whilecovering the surface portion thereof by use of the copper platingsolution in which CNT (or CNF) is dispersed. Thus, the size of the airspace inside the copper powder sintered body 26 can be reduced.

In other words, the size of the air space can be easily controlled byappropriately changing the thickness of the plating wick layer 28 inaccordance with the grain size of the copper powder 26 a. During theprocess, the plating wick layer 28 is formed to partially fill the airspace instead of completely filling the air space (slight air space tomaintain sufficient capillary force is left). Thus, high capillary forceand good circularity of the working fluid can be maintained.

The copper powder sintered body in the state of the art has a problemthat heat conductivity is low as compared with the case of a bulk typedue to the presence of a large number of gaps (air space) as illustratedin FIG. 3B. On the other hand, in the structure of the heat pipe 20(wick layer 24) of the embodiment, the copper plating solution (copperplating layer 28) enters the air space (gaps between grains of thecopper powder 26 a) inside the copper powder sintered body 26 and thenpartially fills the air space as illustrated in FIG. 3A. Accordingly,the structure having high capillary force and excellent circularity ofthe working fluid is implemented.

In addition, the CNT (or CNF) 28 b having a heat conductivity equal toor greater than that of diamond is mixed (dispersed) into the platingwick layer 28 (copper plating solution). Thus, the heat conductivity ofthe wick layer 24 as a whole can be increased. Although depending on theamount of the CNT (or CNF) 28 b to be mixed, an increase ofapproximately 10 to 20% of the heat conductivity can be expected ascompared with the case illustrated in FIG. 1. Here, the heatconductivity of the CNT is around 3000 W/(m·K) while the heatconductivity of the CNF is around 1200 W/(m·K).

In the aforementioned embodiment, an example of the case where the wicklayer 24 (structure in which the copper powder sintered wick layer 26and the CNT mixed copper plating wick layer 28 are combined) is formedover the entire inner wall surface of the metal pipe 22 is described.However, as apparent from the gist of the invention, the wick layer 24does not have to be necessarily formed over the entire inner wallsurface of the pipe 22. Basically, any configuration is sufficient if atemperature gradient sufficient to cause the working fluid (water inthis case) to reflux is formed in the pipe 22.

FIGS. 4A to 4C show an example of such a configuration, and illustrate aconfiguration of a heat pipe according to a modification of theembodiment illustrated in FIGS. 2A to 2C. Here, FIG. 4A shows a verticalcross-sectional structure of the heat pipe 20 a. FIG. 4B shows anenlarged cross-sectional structure of a portion (wick layer 24) denotedby reference sign A in FIG. 4A. FIG. 4C shows an enlargedcross-sectional structure of a portion (sintered wick layer 26) denotedby reference sign B in FIG. 4A.

As compared with the configuration of the heat pipe 20 (FIGS. 2A to 2C)of the aforementioned embodiment, the heat pipe 20 a according to thismodification is different in that the wick layer 24 is formed only atpositions on the inner wall surface of the metal pipe 22 respectivelycorresponding to the portions where the heat pipe 20 a exchanges heatwith the outside (evaporating portion and condensing portionrespectively at both end portions of the pipe). In addition, the heatpipe 20 a is different in that only the copper powder sintered body(sintered wick layer 26) is formed in the other portions of the innerwall surface of the metal pipe 22. The other configuration of the heatpipe 20 a is the same as in the case of the embodiment illustrated inFIGS. 2A to 2C. Accordingly, the description thereof is omitted herein.

A method of manufacturing the heat pipe 20 a is basically the same asthe method used in the aforementioned embodiment. In this modification,the copper powder sintered body (sintered wick layer 26) is first formedon the surface of the required metal plate (metal plate before beingsubjected to a bending process, flattening process and the like to formthe metal plate into a required shape as the hermetically sealed metalpipe) in the same manner as the aforementioned embodiment (see FIG. 4C).However, an appropriate mask (plating resist) is then used to cover aportion on the sintered wick layer 26 except for the positionscorresponding to both end portions of the pipe (evaporating portion andcondensing portion), and the CNT mixed copper plating is applied ontothe portion not covered by the resist to form the plating wick layer 28(see FIG. 4B). Thus, the wick layer 24 is formed only at thecorresponding positions (positions corresponding to the evaporatingportion and the condensing portion at both end portions of the pipe,respectively) on the inner wall surface of the metal pipe 22.

Second Embodiment

In the aforementioned embodiments, described is an example of the casewhere the wick layer 24 is formed of a combined structure including thefirst wick (sintered wick layer 26) of sintered metal type and thesecond wick formed of the plating layer in which CNT or the like ismixed (CNT mixed copper plating wick layer 28), and the second wick isformed by a wet process using plating. However, the method of formingthe wick layer 24 is not limited only to this as a matter of course. Themethod to be described below is another example of the method.

In the second embodiment, a dry process is used to form a sintered wicklayer (wick layer in which CNT (or CNF) is mixed) corresponding to theaforementioned wick layer 24. A technique (Japanese Laid-open PatentPublication No. 2005-343749) previously proposed by the applicant ofthis application can be used for the method of forming the CNT mixtureby sintering.

First, copper powder and CNT are evenly mixed by use of a fast gasmixture technique. In this process, the processing atmosphere ispreferably an inert gas (such as nitrogen gas or argon gas), and thepowder flow rate is preferably set to 50 to 400 Km/H.

Next, the mixture of the copper powder and CNT formed by theaforementioned technique is sintered by using copper pulse electriccurrent sintering with the mixture pressed, by the amount of pressurenot to destroy the copper powder, against and thus put in close contactwith one of surfaces of a required copper plate (copper plate beforebeing subjected to a bending process, flattening process and the like toform the copper plate into a required shape as the metal pipe 22 inwhich a working fluid is eventually encapsulated and hermeticallysealed). Thus, the sintered wick layer (wick layer in which CNT ismixed) is formed. In this process, it is preferable that a vacuum gas ornitrogen gas is used as the processing atmosphere, the temperature ofthe processing atmosphere is between approximately 400 to 1050° C., andpulse current is used as the conduction method.

In the case of using the method according to the second embodiment, theplating process as described in the aforementioned embodiment does nothave to be performed, and all the processes are performed in drycondition. Accordingly, the oxidization of copper or the like isreduced, and a sintered wick layer with high quality and highreliability can be formed.

Furthermore, the aforementioned embodiments are described by taking theheat pipes 20 and 20 a (FIGS. 2A to 2C and 4A to 4C) as examples of theform of heat-radiating component. However, the form of theheat-radiating component is not limited to the examples. For example,the invention is applicable to a vapor chamber which is called aheat-sink type heat pipe.

FIGS. 5A to 5C show an example of such a vapor chamber. FIG. 5A shows anapplication example of a vapor chamber 30. FIG. 5B shows a verticalcross-sectional structure of the vapor chamber 30. FIG. 5C shows anenlarged cross-sectional structure of a portion (wick layer 24) denotedby reference sign A in FIG. 5B.

The vapor chamber 30 is arranged between a semiconductor element (chip)40 such as a CPU and a heat sink 42 as illustrated in FIG. 5A. The chip40 and the heat sink 42 are each bonded to the vapor chamber 30 via anadhesive such as an epoxy-base resin having high heat conductivity.

As compared with the configuration of the heat pipe 20 (FIGS. 2A to 2C)of the aforementioned embodiment, the vapor chamber 30 is only differentin that the vapor chamber 30 includes a metal container 32 instead ofthe metal pipe 22 as illustrated in FIG. 5B. In addition, the internalstructure of the vapor chamber 30 is the same as the internal structureof the heat pipe 20. Thus, the description of the structure is omittedherein.

As illustrated, the vapor chamber 30 efficiently cools the CPU 40 bywidely dispersing the heat generated from the CPU 40 into the heat sink42 having a large cooling area. The amount of heat generation of anelectronic device such as the CPU 40 is expected to increase in thefuture as the performance of such an electronic device furtherincreases. Thus, the vapor chamber 30 is quite effectively used to coolsuch an electronic device.

In addition to the aforementioned type of the vapor chamber in which theheat sink 42 is provided on top of the vapor chamber 30, the types ofvapor chambers include one provided with a heat fin on top of a vaporchamber, one provided with a heat pipe, and the like. In any types ofthe vapor chambers, heat exchange can be efficiently performed between aheat-generating component (semiconductor element such as a CPU) and aheat-radiating component (such as a heat sink, heat fin or heat pipe).

All examples and conditional language recited herein are intended forpedagogical purposes to aid the reader in understanding the inventionand the concepts contributed by the inventor to furthering the art, andare to be construed as being without limitation to such specificallyrecited examples and conditions, nor does the organization of suchexamples in the specification relate to a showing of the superiority andinferiority of the invention. Although the embodiments of the presentinvention have been described in detail, it should be understood thatthe various changes, substitutions, and alterations could be made heretowithout departing from the spirit and scope of the invention.

1. A heat-radiating component comprising: a hermetically sealedcontainer made of metal; a wick layer formed on an inner wall of thehermetically sealed container; and a working fluid encapsulated in thehermetically sealed container, wherein micro carbon fiber is mixed intometal powder in the wick layer.
 2. The heat-radiating componentaccording to claim 1, wherein the wick layer is a structure combined bya first wick and a second wick, the first wick being formed of sinteredmetal powder, and the second wick being a plating layer into which microcarbon fiber is mixed so as to partially fill air space inside the firstwick while covering a surface of the first wick.
 3. The heat-radiatingcomponent according to claim 2, wherein the first wick is a bodysintered copper powder, and the second wick is formed of a copperplating layer into which carbon nanotube or carbon nanofiber is mixed.4. The heat-radiating component according to claim 2, wherein the wicklayer is formed at least at a position on the inner wall of thehermetically sealed container, the position corresponding to a portionwhere the heat-radiating component exchanges heat with outside.
 5. Theheat-radiating component according to claim 1, wherein the wick layer isa sintered wick layer formed by sintering copper powder into whichcarbon nanotube or carbon nanofiber is mixed.
 6. The heat-radiatingcomponent according to claim 5, wherein the wick layer is formed atleast at a position on the inner wall of the hermetically sealedcontainer, the position corresponding to a portion where theheat-radiating component exchanges heat with outside.
 7. Theheat-radiating component according to claim 1, wherein the micro carbonfiber is carbon nanotube or carbon nanofiber.
 8. The heat-radiatingcomponent according to claim 1, wherein the working fluid is water.
 9. Amethod of manufacturing a heat-radiating component which includes a wicklayer formed on an inner wall of a hermetically sealed container made ofmetal and which encapsulates a working fluid in the hermetically sealedcontainer, the method comprising forming the wick layer, wherein theforming the wick layer includes mixing micro carbon fiber into metalpowder.
 10. The method of manufacturing a heat-radiating component,according to claim 9, wherein the forming the wick layer includes:forming a first wick by depositing and then sintering metal powder onone of surfaces of a metal plate before being formed into a requiredshape as the hermetically sealed container; and forming, by use of aplating solution in which micro carbon fiber is dispersed, a second wickso as to partially fill air space inside the first wick while covering asurface portion of the first wick.
 11. The method of manufacturing aheat-radiating component, according to claim 10, wherein copper powderis used as the metal powder in the forming of the first wick, and acopper plating solution in which carbon nanotube or carbon nanofiber isdispersed is used in the forming of the second wick.
 12. The method ofmanufacturing a heat-radiating component, according to claim 9, whereinthe forming the wick layer includes forming a sintered wick layerthrough a dry process by sintering a mixture of copper powder and carbonnanotube or carbon nanofiber with the mixture put in close contact withone of surfaces of a metal plate before being formed into a requiredshape as the hermetically sealed container.
 13. The method ofmanufacturing a heat-radiating component, according to claim 12, whereinthe dry process includes: uniformly mixing the copper powder and thecarbon nanotube or carbon nanofiber by a fast gas mixture technique; andsintering the mixture through copper pulse electric current sinteringwith the mixture pressed against and put in close contact with the oneof surfaces of the metal plate.